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18 October 2004 Trapping nanoparticles with cylindrical polarization
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Metallic and magnetic nano-particles are generally considered difficult to trap due to strong scattering and absorption forces. In this paper, we propose new methods of trapping metallic and magnetic nano-particles using highly focused cylindrically polarized beams. It is shown that an optical tweezers using cylindrical polarization can stably trap metallic/magnetic particles in 3-dimension, owing to the unique focusing properties of cylindrically polarized beams. Metallic particles can be stably trapped by highly focused radial polarization. The extremely strong axial electrical field from a highly focused radially polarized beam provides a large gradient force. Meanwhile, this strong axial field component does not contribute to the Poynting vector along the optical axis. Consequently, it does not create axial scattering/absorption forces. Owing to such a spatial separation of the peaks of gradient force and scattering/absorption forces, a stable 3-D optical trap for metallic nano-particles can be formed. Similarly, an optical tweezers using azimuthal polarization may provide stable 3-D trapping of magnetic nano-particles due to an extremely strong axial magnetic field.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Qiwen Zhan "Trapping nanoparticles with cylindrical polarization", Proc. SPIE 5514, Optical Trapping and Optical Micromanipulation, (18 October 2004);

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